I know that M Dwarf stars emit intense solar flares, which is thought to pose a potential problem for the emergence of life on planets that orbit them. But I was wondering if the life that might exist in the terminator region could be protected from these flares, simply by the angle that the photons would hit the atmosphere, making it so that those higher energy wavelengths would be filtered out.

If the planet were tidally locked to the star, the terminator would be in a (relatively) fixed position, providing some stability to the presence of visible light but shielding from shorter wavelengths and radiation via "$\sec(\theta)$ shielding".

These terminator regions would basically be in a state of perpetual sunset. During evening on Earth, only the longer wavelengths reach us, and we aren't exposed to much (if any?) UV.

Has such a "life at the terminator" scenario ever been addressed scientifically? Are there any obvious problems that would make it impossible?

  • $\begingroup$ @ProfRob I've adjusted the wording to hopefully avoid most of that. $\endgroup$
    – uhoh
    Sep 20, 2022 at 18:46
  • 1
    $\begingroup$ Thank you for adjusting the wording! I appreciate it! $\endgroup$
    – Elhammo
    Sep 20, 2022 at 23:17
  • $\begingroup$ In the videogame Mass Effect 2, there is an interesting depiction of the terminator of an almost tidally locked planet, you can see it in the first minute of this video. According to the authors of the game, the huge temperature difference would create a permanent thunderstorm with exceptionally strong winds. Not the best place to live in $\endgroup$
    – Prallax
    Sep 21, 2022 at 7:37


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